Observation of a to-be-observed specimen through an optical microscope is performed in such a manner that light is irradiated to the to-be-observed specimen, and coming light (reflected light, transmitted light, fluorescent light, etc.) from the to-be-observed specimen is imaged through a lens. Fluorescence microscopes using fluorescent light as the coming light are divided into a non-scanning type and a scanning type. In the non-scanning type fluorescence microscopes, only light (excitation light) having a specified wavelength is irradiated to a to-be-observed specimen to image the fluorescent light emitted from the to-be-observed specimen by a lens, thereby observing the to-be-observed specimen. The wavelength of the fluorescent light emitted from the to-be-observed specimen is different from the wavelength of the excitation light. Accordingly, it is possible to take out only the fluorescent light with a filter or the like to obtain a cross-section image. The scanning type fluorescence microscopes include confocal optical microscopes for obtaining a cross-section image. A confocal optical microscope performs laser scanning on a to-be-observed specimen along a cross-section plane to obtain a point light source coming from the to-be-observed specimen. Since a cross-section image composed of only images in focus is obtainable, an image with less blur can be generated to enable observation of the to-be-observed specimen (PTL 1 and PTL 2).